Fix perl build problems on Stratus VOS

Fix perl build problems on Stratus VOS

The attached text files contain patches to correct build problems on the
Stratus VOS (recently renamed "OpenVOS") operating system. I have tested
these changes on OpenVOS Release 17.0, which is the most-current
customer release. None of these changes should affect any other OS.

Makefile.SH: This patch removes the "miniperl" dependency of the "all"
target. On an operating system that does not require an executable
suffix, the miniperl$(EXE_EXT) dependency evaluates to "miniperl", too.
But on an operating system like VOS that does have an executable suffix,
miniperl$(EXE_EXT) evaluates to (in our case) "miniperl.pm" and the
"miniperl" target is unresolved.

ext/Socket/Socket.xs: Sadly, OpenVOS does not yet support IPv6. I edited
the code to allow for this case, while retaining IPv6 support for
operating systems that do support it.